Device to determine the thickness of a conductive layer

Abstract

The device comprises at least a measuring head ( 7 ) with a transmitter ( 7 A) and a receiver ( 7 B). The head comprises means to measure the thickness through surface resistivity and optical means to measure said thickness by measuring the transparency of the substrate and of the relative layer applied to it.

1. A device for contact free measurement of the thickness of a thin layer coated on a substrate, the device comprising:
 a measuring head including optical means for measuring the thickness of the thin layer coated on the substrate, said optical means measuring the transparency of the substrate and of the relative layer applied to the substrate, said optical means including an optical transmitter and an optical receiver, said optical transmitter and said optical receiver being arranged on opposite sides of said substrate, said optical transmitter and said optical receiver measuring attenuation of an optical signal passing through the substrate, said head comprising surface resistivity means for measuring the thickness of the thin layer coated on the substrate through surface resistivity, said surface resistivity means comprising a transmitter with a transmission coil and a receiver with a receiver coil, said transmitter producing an electromagnetic field, said receiver detecting the electromagnetic field emitted by said transmission coil, said receiver and said transmitter measuring attenuation of said electromagnetic field when electromagnetic field passes through the substrate, said transmitter coil and said receiver coil being arranged on opposite sides of said substrate, the substrate passing between said transmission coil and said receiving coil, said optical transmitter being arranged coaxially with said transmission coil, said optical receiver being coaxially arranged with said receiving coil. 
 
   
   
     2. A device in accordance with  claim 1 , wherein said transmission coil is wound on a bobbin, inside which said optical emitter is positioned. 
   
   
     3. A device in accordance with  claim 1 , wherein said receiver coil is wound on a bobbin, inside which said optical receiver is positioned. 
   
   
     4. A device in accordance with  claim 2 , wherein said optical emitter comprises a light source and a collimation lens. 
   
   
     5. A device in accordance with  claim 3 , wherein said optical receiver comprises a focusing lens and an optical sensor. 
   
   
     6. A device in accordance with  claim 1 , further comprising a plurality of said heads positioned side by side. 
   
   
     7. A device in accordance with  claim 1 , further comprising a main control unit, with which said at least one measuring head is interfaced. 
   
   
     8. A device in accordance with  claim 7 , wherein a plurality of measuring heads are provided, said heads being connected to said main control unit through a serial line. 
   
   
     9. A device in accordance with  claim 7 , wherein both means to measure the thickness through surface resistivity and optical means to measure the thickness by measuring the transparency of the substrate are simultaneously active in each measuring head, and wherein said control unit only processes the data coining from one or other of said measuring means. 
   
   
     10. A device in accordance with  claim 7 , wherein both means to measure the thickness through surface resistivity and optical means to measure the thickness by measuring the transparency are simultaneously active in each measuring head, and wherein said control unit processes the data coining from one or other of said measuring means for the same substrate. 
   
   
     11. A device in accordance with  claim 7 , wherein said main control unit alternately activates the measuring means through surface resistivity or the optical means in each measuring head. 
   
   
     12. A device for contact free measurement of the thickness of a layer coated on a substrate, the device comprising:
 a measuring head having a first part and a second part, said first part being disposed opposite said second part such that said first part and said second part define a space, the substrate being located within said space; 
 an optical means having an optical transmitter arranged in said first part and an optical receiver located in said second part, said optical transmitter emitting light directed at the substrate, said substrate being exposed to said light, said optical receiver detecting attenuation of light after the substrate is exposed to said light, said optical means measuring the transparency of the substrate and the thickness of the layer applied to the substrate via said attenuation of light; 
 a surface resistivity means having a transmitter located within said first part and a receiver arranged in said second part, said transmitter having a transmission coil, said transmitter producing an electromagnetic field, the substrate being exposed to said electromagnetic field, said transmission coil being arranged coaxially with said optical transmitter, said receiver having a receiver coil, said receiver detecting attenuation of said electromagnetic field, said receiving coil being coaxially arranged with said optical receiver, said surface resistivity means determining surface resistivity of the substrate from said attenuation of said electromagnetic field, said surface resistivity means determining the thickness of the layer coated on the substrate via said surface resistivity. 
 
   
   
     13. A device in accordance with  claim 1 , wherein:
 said transmission coil is wound on a first support, said first support having a first support central seat, said optical emitter being positioned inside said first support central seat; 
 said receiver coil is wound on a support, said support having a support central seat, said optical receiver being positioned inside said support central seat; 
 a collimator lens is arranged in front of said optical transmitter, said collimator lens frontally closing said first support central seat; and 
 a focusing lens is arranged in front of said optical receiver, said focusing lens frontally closing said support central seat.